Tool insert

ABSTRACT

A method of producing a tool insert which comprises a central metal portion having edge regions of superabrasive material bonded thereto and presenting cutting edges or points for the tool insert is disclosed. A body ( 50 ) having major surfaces on each of opposite sides thereof, each having spaced strips ( 64 ) of superabrasive material, typically abrasive compact such as PCBN or PCD, for example, separated by a metal region or regions, such as cemented carbide, is provided. Each superabrasive strip of one major surface is arranged in register with a superabrasive strip of the opposite major surface. Alternatively, each superabrasive strip extends from one major surface to the opposite major surface. The body is severed from one major surface to the opposite major surface along at least two sets of planes intersecting at or in the respective superabrasive strips to produce the tool insert.

This application is a 371 of PCT/IB03/00600 filed on Feb. 20, 2003,published on Aug. 28, 2003 under publication number WO 03/070417 A1 andclaims priority benefits of South African Patent Application No. ZA2002/1473 filed Feb. 21, 2002.

BACKGROUND OF THE INVENTION

This invention relates to a tool insert.

Abrasive compacts are polycrystalline masses of abrasive particles,generally ultra-hard abrasive particles, bonded into a hard coherentmass. Such compacts are generally bonded to a substrate, typically acemented carbide substrate. Diamond abrasive compacts are also known asPCD and cubic boron nitride abrasive compacts are also known as PCBN.

U.S. Pat. No. 4,807,402 describes an article comprising a support masssuch as a cemented carbide mass having layers of abrasive compact bondedto each of the upper and lower surfaces thereof.

EP 0 714 719 describes a tool insert comprising first and second layersof abrasive compact bonded to a central or intermediate layer ofcemented carbide, ferrous metal or high melting point metal. The toolcomponent is such that it provides a nose and flank of abrasive compact,the nose and flank providing cutting points and edges for the toolinsert. Such tool inserts may be cut, for example, by electrodischargemachining from an article described in U.S. Pat. No. 4,807,402.

U.S. Pat. No. 5,676,496 describes a metal cutting insert comprising acarbide substrate, and at least one body of superhard abrasive material,such as PCD or PCBN, bonded to an edge surface of the substrate andextending from one side surface to the other side surface of thesubstrate. A plurality of superhard bodies may be disposed at respectivecorners of the substrate. Methods of making similar inserts aredisclosed in U.S. Pat. No. 5,598,621 and U.S. Pat. No. 5,813,105.

A major drawback of the methods of making directly sintered,multicornered inserts described in the prior art is one of scale, with asmall number of cutting tool inserts being produced during a single highpressure, high temperature cycle.

SUMMARY OF THE INVENTION

According to the present invention, a method of producing a tool insertwhich comprises a central metal portion having edge regions ofsuperabrasive material bonded thereto and presenting cutting edges orpoints for the tool insert, includes the steps of:

-   -   (i) providing a body having major surfaces on each of opposite        sides thereof, each major surface having spaced strips of        superabrasive material separated by a metal region or regions,        each superabrasive strip of one major surface being in register        with a superabrasive strip of the opposite major surface or each        superabrasive strip extending from one major surface to the        opposite major surface; and    -   (ii) severing the body from one major surface to the opposite        major surface along at least two sets of planes intersecting at        or in the respective superabrasive strips to produce the tool        insert.

The severing of the body is carried out in such a manner as to exposethe superabrasive strips to form a cutting tip or edge in the toolinsert. For example, the severing of the body may take place along atleast two lines through, and transverse to, at least two of the stripsand also along lines essentially longitudinally through at least twoadjacent strips.

The metal region may be a hard metal such as cemented carbide, a ferrousmetal or a high melting point metal. The metal region is preferablycemented carbide.

The superabrasive material is typically an abrasive compact, preferablyPCD or PCBN, most preferably PCBN.

The body will preferably have a disc shape. The disc will preferablyhave a diameter of from about 55 mm to about 125 mm, more preferablyfrom about 80 mm to about 100 mm, and a thickness of from about 1.6 mmto about 30 mm, more preferably from about 2 mm to about 10 mm.

Severing may take place by known methods, e.g. laser cutting orelectrodischarge machining.

According to another aspect of the invention, there is provided apolyhedral tool insert comprising a central metal portion having majorsurfaces defined on opposite sides thereof, and at least onesuperabrasive strip bonded to each of the major surfaces or extendingfrom the one major surface to the opposite major surface, eachsuperabrasive strip providing the tool insert with a cutting tip oredge. The polyhedral tool insert is preferably star-shaped.

According to a further aspect of the invention, there is provided a toolinsert comprising a central metal portion having major surfaces definedon opposite sides thereof, the central metal portion including centralraised regions extending from the respective major surfaces and loweredregions located about the periphery of the raised regions, and a thinlayer of superabrasive material in the form of a strip bonded to each ofthe major surfaces in the respective lower regions, each superabrasivestrip providing the tool insert with a cutting tip or edge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a perspective view of an embodiment of a body for use in themethod of the invention,

FIG. 1 b is a sectional side view of the body of FIG. 1 a,

FIG. 1 c is a perspective view of a tool insert produced by the methodof the invention,

FIGS. 2 to 9 illustrate further embodiments of the invention with theFigures “a” being perspective views of bodies for use in the method,FIGS. “b” being sectional side views of such bodies, FIGS. “c” beingperspective views of tool insert embodiments and FIGS. “d” beingsectional side views of tool insert embodiments.

DESCRIPTION OF EMBODIMENTS

An embodiment of the invention will now be described with reference toFIG. 1 of the accompanying drawings. Referring first to FIG. 1 a, a body10 in the form of a circular disc comprises alternating regions 12 ofcemented carbide and strips 14 of superabrasive material, in this caseabrasive compact.

The cemented carbide regions 12 and abrasive compact strips 14 arebonded to each other during a high pressure/high temperature sinteringstep. The body 10 has major flat surfaces 16, 18 on each of oppositesides thereof.

The body 10 is severed along spaced lines 20 transverse to the abrasivecompact strips 14. The body is also severed along lines 22longitudinally through each of the abrasive compact strips 14. Severingtakes place right through the body from one major surface 16 to theother major surface 18. The product or tool insert which is produced isillustrated by FIG. 1 c. This insert has a central portion 24 ofcemented carbide to which are bonded longitudinal edge strips 26 ofabrasive compact. The edge strips 26 extend continuously from the onemajor surface 16 to the other major surface 18. A hole 28 may be formedthrough the central portion 24 for mounting the tool insert in a tool.The edges 30 and corners 32 of the abrasive compact strips 26 providethe cutting edges or points for the tool insert.

The body 10 may be made by providing the components, in particulateform, necessary to produce the cemented carbide regions 12, for exampletungsten carbide regions, and the strips 14, for example PCBN, bondedinto coherent form by means of a binder such as an organic binder. Thebody may also be assembled using presintered strips of the hard metal. Agreen state body is produced by suitably locating the regions and stripsin a capsule. The capsule is placed in the reaction zone of aconventional high temperature/high pressure apparatus. Subjecting thegreen state body to suitable elevated temperature and pressureconditions, for example, those at which the abrasive present in thestrips is crystallographically stable, results in a sintered hard andbonded body as illustrated by FIGS. 1 a and 1 b being produced.

The embodiments of FIGS. 2 to 4 are similar to that of FIG. 1 and likeparts carry like numerals. In these embodiments, alternative sever lineconfigurations of patterns are illustrated to produce, respectively, atriangular insert (FIG. 2 c), a polyhedral tool insert having fourcutting tips with included angles less than 90 degrees (FIG. 3 c) and arhombohedral insert (FIG. 4 c). Once again the edge strips 26, orsections thereof, extend continuously from the one major surface 16 tothe other major surface 18.

A further embodiment of the invention will now be described withreference to FIG. 5. Referring first to FIG. 5 a, a cemented carbidebody 50 is of disc shape having major flat surfaces 52, 54 on each ofopposite sides thereof. Each major flat surface has a series of parallelspaced grooves 56 formed therein. Each groove 56 has located therein astrip of superabrasive material, in this case abrasive compact which isbonded to the cemented carbide body.

A tool insert is produced by first severing the body 50 along spacedlines 58 which are transverse to the abrasive compact filled grooves 56from one major surface 52 to the opposite major surface 54. Thereafter,the body is severed in a transverse direction along lines 60 which passlongitudinally through each of the grooves 56. Again, severing takesplace from one major surface 52 to the opposite major surface 54.

The product or tool insert which is produced is illustrated by FIG. 5 c.This insert has a rectangular or square shape and a central portion 62of cemented carbide to which are bonded strips 64 of abrasive compact.The strips 64 are provided along top and bottom edges of opposite sidesof the tool insert. The strips on each side are separated by cementedcarbide in the regions 66. The strips 64 each provide cutting edges 68and cutting points 70. The central cemented carbide region 62 may have ahole 72 formed through it for mounting the tool insert in a tool.

The body 50 may be made by providing a disc shaped cemented carbidebody, for example a tungsten carbide body, and cutting grooves 56 in thetwo major surfaces thereof. The components, in particulate form,necessary to produce the abrasive compact, for example PCBN, are placedin the grooves 56. These particles may be bonded into a coherent form bymeans of a binder such as an organic binder. The cemented carbide body,with the loaded grooves, is placed in the reaction zone of aconventional high temperature/high pressure apparatus. Subjecting thebody to suitable elevated temperature and pressure conditions, forexample, those at which the abrasive present in the strips iscrystallographically stable, results in a sintered hard and bonded bodyas illustrated by FIGS. 5 a and 5 b being produced.

The embodiments of FIGS. 6 to 8 are similar to that of FIG. 5 and likeparts carry like numerals. In these embodiments, alternative sever lineconfigurations of patterns are illustrated to produce, respectively, atriangular insert (FIG. 6 c), a polyhedral tool insert having lowcutting tips with included angles less than 90 degrees (FIG. 7 c) and arhombohedral insert (FIG. 8 c). Once again the edge strips 64, orsections thereof on each side are separated by cemented carbide in theregions 66.

A further embodiment of the invention is illustrated in FIG. 9. Adisc-shaped body of cemented carbide 100 is provided. The body 100 hasmajor surfaces 102 and 104 on each of opposite sides thereof. Eachsurface has scalloped strips 106 formed therein, the scalloped stripsdefining a cross-hatch configuration. Each scalloped strip 106 has athin layer of superabrasive material, in this case abrasive compactbonded to it. The body 100 is severed along lines 108 and transversethereto, lines 110. The tool insert which is produced is illustrated byFIG. 9 c (perspective view) and FIG. 9 d (cross-section). The toolinsert comprises a body 112 of cemented carbide having scalloped edgeregions 114 each of which is provided with a thin layer 116 of abrasivecompact. The edges 118 and corners 120 provide cutting edges and pointsfor the insert. A centrally located hole 122 may be provided through thecemented carbide. The geometry of the tool insert of this embodimentprovides for so-called “chip-breaking” in use.

In the embodiments described above, the severing of the bodies may takeplace by methods known in the art, for example, laser cutting orelectrodischarge machining.

1. A method of producing a tool insert comprising a central metalportion having edge regions of superabrasive material bonded thereto andpresenting cutting edges or points for the tool insert, includes thesteps of: (i) providing a body having major surfaces on each of oppositesides thereof, each major surface having strips of superabrasivematerial separated by a metal region or regions, each superabrasivestrip of one major surface being in register with a superabrasive stripof the opposite major surface or each superabrasive strip extending fromone major surface to the opposite major surface; and (ii) severing thebody from one major surface to the opposite major surface along at leasttwo sets of planes intersecting at or in respective superabrasive stripsto produce the tool insert.
 2. A method according to claim 1, whereinthe metal region is a hard metal selected from the group comprising acemented carbide, a ferrous metal and a high melting point metal.
 3. Amethod according to claim 1, wherein the superabrasive material is anabrasive compact.
 4. A method according to claim 3, wherein the abrasivecompact is PCD or PCBN.
 5. A method according to claim 1, wherein thebody has a disc shape.
 6. A method according to claim 5, wherein thediameter of the disc is from about 55 mm to about 125 mm and thethickness thereof is from about 1.6 mm to about 30 mm.
 7. A methodaccording to claim 6, wherein the diameter of the disc is from about 80mm to about 100 mm and the thickness thereof is from about 2 mm to about10 mm.
 8. A method according to claim 1, wherein a severing pattern isprovided for severing the body to produce a multiple of tool insertshaving a desired shape.